If a body of mass m is carried by a lift moving with an upward acceleration a, then the forces acting on the body are …

Q:  If a body of mass m is carried by a lift moving with an upward acceleration a, then the forces acting on the body are (i) the reaction R on the floor of the lift upward (ii) the weight mg of the body acting vertically downwards. The equation of motion will be given by

(a) R = mg – ma

(b)R = mg + ma

(c) R = ma – mg

(d) R = mg × ma

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Ans: (b)

Sol: R – m g = m a

R = m g + m a